I recommend a good light armor set (I used Theca, being cheaper than Drake). Weapon -- probably a homonkulus with Acumen. You'll do better off continuing to nuke until the 50s, so you can wait on a melee weapon until B grade. You'll probably wanna keep the sword, too, as there are times you'll want the cast speed.
matter of fact, you could get by with a robe set (divine for casting speed or demon for nuking power) until 48 or so. around then you'll want ot switch from nuke to tank. drake or theca, focus'ed sword or health blunt, one handed either way as you'll want a shield. you'll still do a lot of damage in comparison to your summon well into your 50's and low 60's.
I would think if you are fighting mobs right around your level that spells would begin to fail around 42 or so since they are 7 levels below at that point or is it based solely on the character's level and damage amount is just reduced?
I was looking forward to switching to more melee at 40 but it seems that might not be the best idea.
with bsps usage your spells will still work reasonably well up until 52, and will still do half damage for a while after that. until they nerfed sleep, I used to be able to land that about 2/3 the time even when I hit 50. I still land it 2/3 the time, it is just useless to cast now.
the problem with melee at low levels as a summoner is that your summon will have less pattk than you until 48. usually, dropping a nuke on a mob and then having the summon finish it off works real well until you hit 48 or so, then you can go melee with increasing degrees of success.